As for the background of the invention, in the manufacture of sanitary articles such as diapers, napkins and pantyliners, various webs of nonwoven fabric and film are wound off supply rolls or bales and combined and united by way of corresponding web guides, with various working operations taking place on the way. Then detachment of individual pieces of the web takes place for configuration of the virtual product.
Problems posed in these manufacturing processes include the comparatively high velocities of the web of several meters per second and the great number of deflectors, conveying rollers and the like for the webs of strip material that frequently have only few centimeters of width. Conditioned by these circumstances, so-called twisters occur as the web winds off and flaps to and fro, in particular in the case of “festooned” supplies—which is a long web of material placed in loops one on top of the other. These twisters can proceed in the running direction via web guides such as deflection rollers, guide gaps etc. so that the twister will ultimately be found in the final product.
Problems arise from the fact that, mostly, at least some of the webs of a multilayer product have definitely allocated top and bottom sides. For example, the impermeable outer layers of diapers often have imprints suitable for children which a twister would turn upside down in the diaper. Another example is the punched cover film in pantyliners which also must be placed correctly during manufacture—i.e. with the projections from punching turned inwards.
A twister that has ultimately passed into the assembly operation of the individual webs will lead to a faulty waste product.
Another problem posed by twisters resides in that the web, where twisted, is exposed to increased strain by the twisting. Furthermore, web guide elements, such as guide gaps, offer some resistance when the twisters pass along, which means additional strain on the web. In this regard, twisters also cause an increase in web rupturing in the manufacturing plant, meaning standstill, downtime and renewed charging, which considerably affects manufacturing efficiency.
It is an object of the invention to embody an apparatus for detecting and eliminating a twister in a running web of flexible material.